TACONIC SYSTEM. 23 



border of Massachusetts and through Vermont, often rising to the height of fifteen 

 hundred feet, known as the Taconic range, furnished the name to this System. 

 It crosses the Hudson about thirty miles above New York City, and passing south 

 through New Jersey, enters Pennsylvania. 



4. Sparry limestone, a name given to it many years before by Prof. Amos 

 Eaton. It occupies a belt of country in the eastern part of Dutchess, Columbia, 

 Rensselaer, and Washington Counties, and passing north strikes the west line of 

 Arlington, Vermont. 



5. Taconic slate, with its subordinate beds of roofing-slate and coarse brecci- 

 ated layers, occupies almost the whole of Columbia, Rensselaer, and Washington 

 Counties, and extends to the base of the Taconic range, which separates New York from 

 Vermont and Massachusetts, and has an immense thickness. It crosses the Hudson 

 above Newburg, and passes through Orange County into New Jersey. From the 

 roofing-slate he defined Diplograptus simplex, and from the Taconic slate in Washing- 

 ton County Bythotrephis flexuosa, B. rigida, Palceochorda marina, Nemapodia tenuissima, 

 Nereites deweyi, N. gracilis, N. jacksoni, N. lanceolatus, N. loomisi, N. pugnus, Myrianites 

 murchisoni, and M. sillimani. 



6. Black slate, forming, so far as he knew, the highest member of the Taconic 

 System, and from which he defined EUiptocephala asaphoides and Atops trilineattis. 



§ 40. He identified the Smithfield limestone in Rhode Island with the Stock- 

 bridge limestone, and an accompanying slate with the Magnesian Slate, and in Black- 

 stone Valley found the brown sandstone and fine granular quartz. He recognized 

 in the slates at Waterville, Maine, the Taconic Slate of New York, and found the 

 Nereites at Kennebec. The fine roofing-slates on the Piscataqua he found subor- 

 dinate to the Taconic Slate, in like manner as they exist in New York. And, jointly 

 with Douglas Houghton, the Taconic System was found largely developed in the 

 Upper Peninsula of Michigan ; the slates of the formation with their fucoidal im- 

 pressions and the granular quartz were both recognized. In 1846, he reproduced 

 his work on the Taconic System in a book on the Agriculture of New York, with 

 an appendix describing a conglomerate at the base, resting unconformably upon 

 granite rocks. 



§ 41. In this manner this geological subdivision was first determined, defined, 

 and established, and it should have been recognized from that time forward. But 

 others, much less informed, disputed the existence of the rocks, erroneously referred 

 his fossils to more recent genera ; and some, finding the same rocks, gave them differ- 

 erent names, which added to the confusion, and seriously retarded the progress of 

 knowledge respecting them. It may be later researches have not, in every respect, 

 sustained his determinations, but Ford's work near Albany, New York, where the 

 position taken by Emmons was most violently assaulted, has not only corroborated 

 him, but has forever set the questions at rest in that locality. Wing, Dale, 

 Marcou, and Dwight have sustained his assertions respecting the want of conform- 

 ability of the Hudson River Slates with the Taconic. All the surveys of Michi- 

 gan and Wisconsin have sustained him, though the geologists apply the later 

 name, Huronian, to the Strata. His determinations of the rocks in North Carolina 

 have been most fully confirmed by later geologists, though some use the word 

 Huronian when referring to them. 



§ 42. In 1849, Alexander Murray, an assistant on the Geological Survey of 



